Holder for cartridge-type electric fuses

ABSTRACT

The closure of a post-type holder for a cartridge-type electric fuse has a cylindrical contact which receives one of the ferruletype terminals of that cartridge-type electric fuse and which has an integrally-formed finger with an inwardly-inclined free end which engages that ferrule-type terminal. A helical compression spring is disposed within that cylindrical contact, and the inwardly-inclined free end of that finger prevents accidental separation of that helical compression spring from that cylindrical contact.

United States Patent 1191 mun.

' Urani 1 Jan. 28, 1975 HOLDER FOR CARTRIDGE-TYPE 3.268.693 8/]966 Linton 337/195 3.299.236 l/l967 Burkcr 337/2l4 X [75] Inventor: Angelo Uram, St. Louls, Mo. Primary liwmimlr oi Harris [73] Assignec: McGraw-Edison Company, Elgin. Almrney, Agent, or Firm-Rogers. Ezcll & Eilers Ill.

[22] Filed: Dec. 14, 1973 ABSTRACT App! 424669 The closure of a post-type holder for u cartridge-type electric fuse has a cylindrical contact which receives [52] U.S. C1. 337/214, 337/228 one Of the yp rmin l f that cartridge-type [51] Int. Cl. H0lh 85/50 electric fuse and which has an integrally-formed finger 58 Field of Search 337/195, 201, 214, 228 with an inwardly-inclined free end which engages that ferrule-type terminal. A helical compression spring is [56] References ci d disposed within that cylindrical contact. and the in- UNITED STATES PATENTS wardly-inclined free end of that finger prevents acci- 2,207,1137 7/1940 Sundt 337 210 x g i i figg'z f wmpress'on Sprmg 2.831.087 4/1958 Sundt 337/201 X mm Cy r 0 2,989,610 6/1961 Linton 337/201 x 3,236,974 2/1960 Loudcn ct 0| 337/195 6 Claims, 5 Drawing Figures Patented Jan. 28, 1975 HOLDER FOR CARTRIDGE-TYPE ELECTRIC FUSES BACKGROUND OF THE INVENTION The closures of post-type holders for cartridge-type electric fuses frequently have cylindrical contacts incorporated therein, and one such closure is shown in US. Pat. No. 2,668,215. In addition the closures, of the post-type holders for cartridge-type electric fuses which the assignee of this application previously sold under the mark I-ITA, included cylindrical contacts which had helical compression springs therein and which had chord-like springs that engaged the ferruletype terminals of the cartridge-type electric fuses.

SUMMARY OF THE INVENTION The closure of the post-type holder, for a cartridgetype electric fuse, which is provided by the present invention has a cylindrical contact that has an integrallyformed finger with an inwardly-inclined free end which directly engages one of the ferrule-like terminals of that electric fuse. Because that finger is formed so it is integral with that cylindrical contact, there is no contact resistance between that finger and that cylindrical contact. That finger is formed so it has two elongated sides, as well as its free end, which are movable relative to that cylindrical contact; and hence that free end can easily be bent outwardly by one of the ferrule-type terminals of the cartridge-type electric fuse as that ferrulelike terminal is moved inwardly of that cylindrical contact. The portion of the inner surface of the cylindrical contact which is diametrically opposite that finger is smooth and has a curvature that is substantially complementary to the curvature of the ferrule-like terminal; and hence that ferrule-like terminal can respond to the laterally-directed forces which that finger will apply to it to experience essentially line-to-line contact with that portion of the inner surface of the cylindrical contact. The free end of the finger can tend to bite into the ferrule-like terminal of the cartridge-type electric fuse, and thus can assure good electrical contact between itself and that ferrule-like terminal. That free end also will act as a stop which will prevent accidental separation of the helical compression spring from that cylindrical contact.

BRIEF DESCRIPTION OF THE DRAWING In the drawing,

FIG. 1 is a side elevational view of a post-type holder, for a cartridge-type electric fuse, which has a closure that includes a cylindrical contact which is made in accordance with the principles and teachings of the present invention.

FIG. 2 is a side elevational view of the closure of that post-type holder and of the left-hand end of a cartridgetype electric fuse which is held by the cylindrical contact of that closure,

FIG. 3 is a sectional view, on a larger scale, through the closure of FIG. 2, and it is taken along the plane indicated by the line 3-3 in FIG. 2,

FIG. 4 is a sectional view which is similar to the sectional view of FIG. 3 but which shows the closure as it appears when the cartridge-type electric fuse has been separated from the cylindrical contact of that closure, and

FIG. 5 is an elevational view, on the scale of FIG. 3, of the inner end of the closure of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing in detail, the numeral 20 denotes the body of a post-type holder, for cartridge-type electric fuses; and that body will preferably be made from a dimensionally-stable dielectric material. The numeral 22 denotes a thread on the outer surface of that body, and the numeral 24 denotes a flat surface which interrupts that thread; and that flat surface enables the body 20 to be inserted within a D-hole in a panel. The numeral 26 denotes a terminal which can be connected to an electrical circuit by a conductor, not shown; and the numeral 28 denotes a further terminal which can be connected to that electrical circuit by a further conductor, not shown. The numeral 30 denotes a cylindrical portion which defines an open end for the body 20; and that cylindrical portion will be disposed forwardly of the panel in which the body 20 is mounted. The numeral 32 denotes a shoulder between the cylindrical portion 30 and the thread 22; and the numeral 34 denotes a resilient washer which is telescoped over that thread and which abuts that shoulder. The numeral 36 denotes a nut which is releasably held by the thread 22. A generally U-shaped stationary contact, not shown, is mounted within the cylindrical portion 30 of the body 20; and that generally U-shaped stationary contact could be similar to the generally U- shaped stationary contact in US Pat. No. 2,668,215. The body 20 is, and has been, commercially available; and it is not, per se, a part of the present invention.

The numeral 60 denotes projections at each side of the free edge of a cylindrical contact 64 which is part of a detachable closure 62 for the open end of the body 20. The numeral 58 denotes outward deformations of the cylindrical contact 64 that are contiguous with the projections 60. The numeral 66 denotes axiallyextending, circumferentially-spaced ribs on the closure 62; and the numeral 68 denotes a reduced-diameter portion of that closure. The numeral 72 denotes a helical compression spring which is telescoped within the cylindrical contact 64, as shown particularly by FIGS. 4 and 5. The closure 62, the projections 60, the outward deformations 58, the ribs 66, the reduceddiameter portion 68 and the spring 72 are not, per se,

, parts of the present invention.

The cylindrical contact 64 has an elongated finger 70 which is integral with that cylindrical contact; and that finger preferably will be formed by a punching, lancing or similar operation after that cylindrical contact has been formed. That finger includes inwardly into the interior of that cylindrical contact, as shown particularly by FIGS. 4 and 5; and that finger coacts with the wall of that cylindrical contact to subtend an acute angle. The free end and the two elongated sides of that finger are physically separated from the wall of that cylindrical contact; and hence that free end and those two elongated sides are movable relative to that cylindrical contact. The inner surface of the opposite side of the cylindrical contact 64 is smooth and uninterrupted, as shown by FIGS. 4 and 5. Because the finger 70 is integral with the cylindrical contact 64, there will be no contact resistance between that finger and that cylindrical contact. Because the free end of that finger is disposed inwardly of the inner surface of that cylindrical contact, that finger will act as a stop to prevent accidental separation of the helical compression spring 72 from that cylindrical contact. The finger 70 is displaced to the right of the free edge of the cylindrical contact 64, as shown by FIGS. 2-4; and hence that cylindrical contact has an uninterrupted, albeit not straight, annular portion adjacent that free edge which keeps that free edge substantially circular. The free end of that finger will be arcuate in cross section and it will have a raw, unpolished lower edge.

The free end, and the major portion of the length of the inner surface, of the finger 70 lie in the path of the ferrule-type terminal 78, of a cartridge-type electric fuse 74, which is to be telescoped into the cylindrical contact 64. The other ferrule-type terminal of that electric fuse is denoted by the numeral 76.

The cylindrical contact 64 is generally circular in cross section. However, the diametral distance between those portions of the wall of that cylindrical contact which include the outward deformations 58 and the projections 60 is slightly longer than the diametral dis tance between that portion of that wall which includes the finger 70 and that portion of that wall which confronts that finger. Specifically, the diametral distance between the portions of the wall of the cylindrical contact 64 which include the outward deformations 58 and the projections 60 is approximately three hundred and two thousandths of an inch, whereas the diametral distance between that portion of that wall which includes the finger 70 and that portion of that wall which confronts that finger is approximately two hundred and eighty-two thousandths of an inch. The approximate diameter of the ferrule-like terminal 78 is two hundred and fifty-two thousandths of an inch; and hence the free end of the finger 70 can extend inwardly of the inner surface of the cylindrical contact 64 only three hundredths of an inch when that ferrule-like terminal is telescoped into that cylindrical contact.

Until the ferrule-type terminal 78 is introduced into the cylindrical contact 64, a portion of the outer turn of the helical compression spring 72 will confront the free end of the finger 70, as shown by FIG. 4. Consequently, that free end of that finger will prevent accidental separation of that helical compression spring from that cylindrical contact. As that ferrule-type terminal is introduced into that cylindrical contact, the inner surface of the inclined finger 70 will be engaged .by that ferrule-type terminal; and the shallow inclination of that finger will facilitate the bending of that finger to the position shown by FIG. 3. As that finger bends from the position shown by FIG. 4 to the position shown by FIG. 3, strong restorative forces will be developed within that finger; and those strong restorative forces will provide good electrical contact between that finger and one side of the ferrule-type terminal 78. In addition, those strong restorative forces will force the opposite side of that ferrule-type terminal into good electrical contact with the opposed portion of the inner surface of the cylindrical contact 64. The resulting electrical contact between the ferrule-type terminal 78 and the finger 70 and the opposed inner surface of the cylindrical contact 64 will be so intimate that the posttype fuseholder which is constituted by the body and by the closure 62 can be given a 20 ampere rating.

The projections 60 on the cylindrical contact 64 will releasably engage a generally U-shaped contact, not shown, of standard and usual design within the body 20, wheneverthe closure 62 is assembled with that body. That U-shaped contact will be connected to the terminal 28; and hence can connect the cylindrical contact 64 to one side of an electrical circuit. The ferrule-type terminal 76 will engage a contact, not shown, within the body 20 which is connected to the terminal 26. As a result, current will flow from terminal 26 via the contact, not shown, which is connected to that terminal, the ferrule-type terminal 76, the fusible element, not shown, within the electric fuse 74, the ferrule-type terminal 78, the finger and also the confronting portion of the cylindrical contact 64, the projections 60, and the U-shaped contact, not shown, within the body 20 to the terminal 28. The helical compression spring 72 will be compressed as the closure 62 is secured to the body 20 of the fuseholder; and the resulting restorative forces in that helical compression spring will provide and maintain good electrical contact between the ferrule-type terminal 76 and the contact, not shown, which is within the body 20 and which is connected to the terminal 26.

The finger 70 is important for several reasons. In the first place, it is integral with the cylindrical contact 64, and thereby obviates any and all contact resistance between itself and that cylindrical contact. In the second place, that finger coacts with the wall of that cylindrical contact to subtend an acute angle; and hence that finger is readily bendable from the position of FIG. 4 to the position of FIG. 3 as the ferrule-type terminal 78 is telescoped into that cylindrical contact. In the third place, that finger directly engages the ferrule-type terminal 78 at a shallow angle; and hence when the helical compression spring 72 shifts that ferrule-type terminal to the left-as it will do during the positioning of the projections 60 behind the U-shaped contact, not shown, within the body 20, the free end of the finger 70 will tend to bite into the surface of that ferrule-type terminal. In the fourth place, that finger will force the opposite surface of the ferrule-type terminal 78 into intimate contact with the opposite side of the inner surface of the cylindrical contact 64. In the fifth place, that finger will prevent accidental separation of the helical compression spring 72 from that cylindrical contact. The overall result is that there will be at least line-to-line contact between the ferrule-type terminal 78 and the inner surface at one side of the cylindrical contact 64, and there will be a line-to-line contact of the bite type between the free end of the finger 70 and the opposite side of that ferrule-type terminal and yet that ferrule-type terminal can easily be inserted into that cylindrical contact. The finger 70 thus makes the electrical contacts between the cylindrical contact 64 and the ferrule-type terminal 78 predictable and consistent to a desirable degree.

Because of finger 70 is formed by a punching, lancing or similar operation, the position of that finger intermediate the outward deformations 58 is fixed and is not a function of the skill or care of an assembler. Similarly, the fact that the finger 70 will confront a smooth, uninterrupted portion of the inner surface of the cylindrical contact 64 is assured and is not a function of the skill or care of an assembler. Moreover, because the free end and the two elongated sides of that finger are actually severed from the wall of that cylindrical contact, it is possible to establish, with a high degree of predictability, the initial inwardly-inclined position of that finger relative to the axis of that cylindrical contact. In contrast, where portions of the wall of a cylindrical contact have merely been deformed beyond their elastie limits, it is not possible to establish, with such a high degree of predictability, the initial positions of those portions.

By making the finger 70 elongated and it is more than four times as long as it is wide it is possible to incline that finger inwardly of the cylindrical contact 64 at a shallow angle and yet dispose the free end and a substantial portion of the inner surface of that finger in the path of the ferrule-type terminal 78. That shallow inclination facilitates easy and simple insertion of that ferrule-type terminal into the cylindrical contact", and the initial positioning of a substantial portion of the inner surface of that finger in the path of that ferruletype terminal enables that finger to develop substantial restorative forces therein as that ferrule-type terminal is moved into that cylindrical contact.

The intimacy of the electrical contacts which the finger 70 causes to be developed between the cylindrical contact 64 and the ferrule-type terminal 78 is great enough to shunt a major part of the current away from the helical compression spring 72. However, if it ever became desirable to effectively isolate that helical compression spring from all current flow therethrough, a disc of insulating material could be telescoped into the inner end of the cylindrical contact 64 before that helical compression spring was telescoped into that cylindrical contact.

Whereas the drawing and accompanying description have shown and described a preferred embodiment of the present invention, it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, a mass of insulating material encasing one end of said cylindrical contact but being spaced away from the other end of said cylindrical contact, said other end of said cylindrical contact projecting outwardly from said mass of insulating material and being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, and an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal ofsaid cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to tend to bite into the surface at one side of said ferrule-type terminal of said cartridgetype electric fuse and also to force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact.

2. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, a mass of insulating material encasing one end of said cylindrical contact but being spaced away from the other end of said cylindrical contact, said other end of said cylindrical contact projecting outwardly from said mass of insulating material and being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to tend to bite into the surface at one side of said ferrule-type terminal of said cartridgetype electric fuse and also to force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact, said other end of said cylindrical contact being a continuous ring and having an uninterrupted portion, and said elongated finger being in register with and being spaced axially inwardly relative to said uninterrupted portion of said continuous ring.

3. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, one end of said cylindrical contact being external of said holder for cartridge-type electric fuses whenever said closure is assembled with said holder for cartridge-type electric fuses, the other end of said cylindrical contact being disposed within said holder for cartridge-type electric fuses whenever said closure is assembled with said holder for cartridge-type electric fuses, said other end of said cylindrical contact being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridgetype electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferruletype terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to apply pressure to the surface at one side of said ferrule-type terminal of said cartridge-type electric fuse and thereby force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact, a helical compression spring located within said cylindrical contact adjacent said one end of said cylindrical contact, said intimate engagement of said surface at said opposite side of said ferrule-type terminal of said cartridge-type electric fuse with said uninterrupted portion of said inner surface of said cylindrical contact enabling said cylindrical contact to shunt a major portion of the current away from said helical compression spring, and said free end of said elongated finger normally acting as a stop to prevent accidental separation of said helical compression spring from said cylindrical contact.

4. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, one end of said cylindrical contact being external of said holder for cartridge-type electric fuses whenever said closure is assembled with said holder for cartridge-type electric fuses, the other end of said cylindrical contact being disposed within said holder for cartridge-type electric fuses whenever said closure is assembled with said holder for cartridge-type electric fuses, said other end of said cylindrical contact being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridgetype electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferruletype terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to apply pressure to the surface at one side of said ferrule-type terminal of said cartridge-type electric fuse and thereby force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact, said free end of said elongated finger being arcuate in end view, and the curvature of said free end of said elongated finger being close to the curvature of said ferruletype terminal of said cartridge-type electric fuse, whereby said free end of said elongated finger can providev more than mere point contact with said ferruletype terminal of said cartridge-type electric fuse.

5. A closure as claimed in claim 1 wherein'said free end of said elongated finger has a raw, un-polished lower edge which can tend to bite" into the surface of said ferrule-type terminal of said cartridge-type electric fuse.

6. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, a mass of insulating material encasing one end of said cylindrical contact but being spaced away from the other end of said cylindrical contact, said other end of said cylindrical contact projecting outwardly from said mass of insulating material and being open and being substantially circular; in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridgetype electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to tend to bite into the surface at one side of said ferrule-type terminal of said cartridge-type electric fuse, said cylindrical contact having circumferentiallyspaced outward deformations adjacent said other end thereof, said elongated finger inclining inwardly from a portion of the wall of said cylindrical contact which is located intermediate said outward deformations, a further portion of said wall of said cylindrical contact being intermediate said outward deformations and being diametrally opposite to the first said portion of said wall of said cylindrical contact, said further portion of said wall being smooth and uninterrupted, and said elongated finger also responding to said restorative forces therein to apply a pressure to said one side of the surface of said ferrule-type terminal of said cartridgetype electric fuse which forces the opposite side of said surface of said ferrule-type terminal of said cartridgetype electric fuse into intimate engagement with said further portion of said wall of said cylindrical contact. n 

1. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, a mass of insulating material encasing one end of said cylindrical contact but being spaced away from the other end of said cylindrical contact, said other end of said cylindrical contact projecting outwardly from said mass of insulating material and being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, and an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to tend to ''''bite'''' into the surface at one side of said ferrule-type terminal of said cartridge-type electric fuse and also to force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact.
 2. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, a mass of insulating material encasing one end of said cylindrical contact but being spaced away from the other end of said cylindrical contact, said other end of said cylindrical contact projecting outwardly from said mass of insulating material and being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled wiTh said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to tend to ''''bite'''' into the surface at one side of said ferrule-type terminal of said cartridge-type electric fuse and also to force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact, said other end of said cylindrical contact being a continuous ring and having an uninterrupted portion, and said elongated finger being in register with and being spaced axially inwardly relative to said uninterrupted portion of said continuous ring.
 3. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, one end of said cylindrical contact being external of said holder for cartridge-type electric fuses whenever said closure is assembled with said holder for cartridge-type electric fuses, the other end of said cylindrical contact being disposed within said holder for cartridge-type electric fuses whenever said closure is assembled with said holder for cartridge-type electric fuses, said other end of said cylindrical contact being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to apply pressure to the surface at one side of said ferrule-type terminal of said cartridge-type electric fuse and thereby force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact, a helical compression spring located within said cylindrical contact adjacent said one end of said cylindrical contact, said intimate engagement of said surface at said opposite side of said ferrule-type terminal of said cartridge-type electric fuse with said uninterrupted portion of said inner surface of said cylindrical contact enabling said cylindrical contact to shunt a major portion of the current away from said helical compression spring, and said free end of said elongated finger normally acting as a stop to prevent accidental separation of said helical compression spring from said cylindrical contact.
 4. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, one end of said cylindrical contact being external of said holder for cartridge-type electric fuses whenever said closuRe is assembled with said holder for cartridge-type electric fuses, the other end of said cylindrical contact being disposed within said holder for cartridge-type electric fuses whenever said closure is assembled with said holder for cartridge-type electric fuses, said other end of said cylindrical contact being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger confronting a smooth and uninterrupted portion of said inner surface of said cylindrical contact, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to apply pressure to the surface at one side of said ferrule-type terminal of said cartridge-type electric fuse and thereby force the surface at the opposite side of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said smooth and uninterrupted portion of said inner surface of said cylindrical contact, said free end of said elongated finger being arcuate in end view, and the curvature of said free end of said elongated finger being close to the curvature of said ferrule-type terminal of said cartridge-type electric fuse, whereby said free end of said elongated finger can provide more than mere point contact with said ferrule-type terminal of said cartridge-type electric fuse.
 5. A closure as claimed in claim 1 wherein said free end of said elongated finger has a raw, un-polished lower edge which can tend to ''''bite'''' into the surface of said ferrule-type terminal of said cartridge-type electric fuse.
 6. A closure, for a holder for cartridge-type electric fuses, which has a cylindrical contact that is dimensioned to readily accommodate a ferrule-type terminal of a cartridge-type electric fuse, a mass of insulating material encasing one end of said cylindrical contact but being spaced away from the other end of said cylindrical contact, said other end of said cylindrical contact projecting outwardly from said mass of insulating material and being open and being substantially circular in end view to readily accommodate said ferrule-type terminal of said cartridge-type electric fuse, an elongated finger which is integral with said cylindrical contact and which constitutes a portion of the wall of said cylindrical contact that has been severed from the rest of said wall of said cylindrical contact at the free end thereof and along the elongated sides thereof, said elongated finger inclining inwardly relative to the inner surface of said cylindrical contact at an acute angle, said elongated finger normally lying in the path of said ferrule-type terminal of said cartridge-type electric fuse but being movable out of the path of said ferrule-type terminal of said cartridge-type electric fuse as said cartridge-type electric fuse is assembled with said closure, said elongated finger responding to movement out of the path of said ferrule-type terminal of said cartridge-type electric fuse to develop restorative forces therein which will cause said free end of said elongated finger to tend to ''''bite'''' into the surface at one side of said ferrule-type terminal of said cartridge-tYpe electric fuse, said cylindrical contact having circumferentially-spaced outward deformations adjacent said other end thereof, said elongated finger inclining inwardly from a portion of the wall of said cylindrical contact which is located intermediate said outward deformations, a further portion of said wall of said cylindrical contact being intermediate said outward deformations and being diametrally opposite to the first said portion of said wall of said cylindrical contact, said further portion of said wall being smooth and uninterrupted, and said elongated finger also responding to said restorative forces therein to apply a pressure to said one side of the surface of said ferrule-type terminal of said cartridge-type electric fuse which forces the opposite side of said surface of said ferrule-type terminal of said cartridge-type electric fuse into intimate engagement with said further portion of said wall of said cylindrical contact. 